1. Field of the Invention
The present invention relates to a light emitting device using an electroluminescent material that can emit laser light.
2. Description of the Related Art
A semiconductor laser has a merit that a laser oscillator can be miniaturized and reduced in weight drastically, as compared with a gas or solid-state laser. Thus, a semiconductor laser comes into practical use in various fields, as a light-source for receiving and transmitting a signal by an optical interconnection in an optical integrated circuit, a light-source for recording in a recording medium such as an optical disk or an optical memory, and a light-source for optical communications using fiber-optics or the like as a optical wave guide. The oscillation wavelength of a semiconductor laser has a wide range of from the blue wavelength to the infrared wavelength. Many semiconductor lasers that are used generally have their oscillation wavelengths in an infrared region, for example, the wavelength of a GaAs laser is 0.84 μm, the wavelength of an InAs laser is 3.11 μm, the wavelength of an InSb laser is 5.2 μm, the wavelength of a GaAlAs laser is 0.72 to 0.9 μm, and the wavelength of an InGaAsP laser is 1.0 to 1.7 μm.
In recent years, many researches on a practical use of a semiconductor laser having the oscillation wavelength in a visible region have been made. Depending on the trend, a laser oscillator that can emit laser light by using an electroluminescent material that can produce electroluminescence by being applied with an electric field (an organic semiconductor laser) has been attracting more attentions. An organic semiconductor laser is expected to have a variety of use, since the organic semiconductor laser can emit laser light whose wavelength is in a visible region and it can be formed over an inexpensive glass substrate.
Reference 1 describes an organic semiconductor laser of which peak wavelength λ is 510 nm (Reference 1: Japanese Patent Laid Open No. 2000-156536. p. 11).
Laser light emitted from an organic semiconductor laser is generally lower in the directivity and easier to diffuse than laser light emitted from other lasers. When the directivity of laser light is low, receiving and transmitting a signal in an optical interconnection becomes unstable due to disclination, and thus, high integration of an optical integrated circuit is prevented, which is not preferable. When diffusion of laser light is large, it is difficult to assure the energy density of the laser light. A desired energy density can be assured by enhancing the intensity of laser light emitted from a light-source or by shortening the distance between the light-source of the laser light and a predetermined region. However, the former has a demerit of increasing power consumption and the latter has a demerit of limiting the use application of the organic semiconductor laser.
The directivity of laser light can be enhanced by providing an optical system prepared separately for an organic semiconductor laser that serves as a light-source is However, as the optical system is more complicated, an adjustment of the optical system in maintenance or positioning of the optical system and the organic semiconductor laser is more troublesome. Further, there is also a defect that resistance to a physical impact gets worse.